DNA REPLICATION

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DNA REPLICATION

• Chapter 11, Section 1

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DNA Review

• What is the building block of DNA?
• Nucleotides
• What is the shape of DNA?
• Double Helix
• What holds together the two strands of DNA?
• Hydrogen bonds between complimentary nitrogen
  base pairs
• During what part of the Cell Cycle does DNA
  replicate (copy itself)?
• Interphase (S phase)
• What pairs with Guanine? Adenine?
• Guanine Cytosine, Adenine Thymine
• What are the complimentary bases for the
  following sequence? AATCCGC
• TTAGGCG

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How DNA Replicates

• DNA has to be replicated before a cell divides
  (during S phase of interphase).
• New cells at the end of Mitosis need identical
  strands of DNA

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• One strand of DNA gets used as a template
  (pattern) to make a new strand that matches up
  with it.
• This is called semi-conservative replication, one
  strand is new and the other is old.
• Special enzymes are required for DNA replication

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Steps of DNA Replication

• 1. Replication begins with the unwinding
  separation of the DNA double helix by enzymes
  called helicases
• The process is like unzipping a zipper

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• 2. New strands are formed by enzymes called DNA
  polymerase which adds complimentary nucleotides
  to the original strands

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• Each new strand compliments one of the original
  strands (one new strand and one old strand
  semi-conservative replication)
• 2 identical DNA double helix strands are the
  result of DNA replication

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Uneven formation of DNA

• When DNA is replicating one strand forms
  continuously and the other strand forms in chunks
  (Okazaki fragments) with spaces that need to be
  filled in.
• Because they form in opposite directions
• Continuously leading strand Chunks lagging
  strand

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• http//www.mcb.harvard.edu/losick/images/trombonef
  inald.swf
• http//www.stolaf.edu/people/giannini/flashanimat/
  molgenetics/dna-rna2.swf
• http//www.wiley.com/college/pratt/0471393878/stud
  ent/animations/dna_replication/index.html